Encrypted databases provide data protection (security) in cloud platforms and/or database-as-a-service settings. In encrypted databases, data can be encrypted at the client and can be provided to the database for storage. Searchable encryption enables data to be encrypted, while still enabling search for keywords.
Searchable encryption is an active area of research and a number of schemes with different efficiency and security characteristics have been proposed. Currently proposed searchable encryption schemes, however, suffer from various drawbacks. In some examples, current searchable encryption schemes either deteriorate from semantic security to the security of deterministic encryption (e.g., under update operations), require information to be stored on the client, and relatively large index sizes are required for deleted files and keywords. All of this is problematic, because the majority of data is expected to be added later or changed. Because such searchable encryption schemes are also less efficient than deterministic encryption, they are currently an unfavorable choice for encryption in the cloud.